Biological Evaluation of Novel 2-Benzimidazole Derivatives for Antibacterial Activity
Infectious diseases remain a persistent global health burden, with bacterial infections accounting for a substantial disease burden. The increasing prevalence of antimicrobial resistance has emphasised the need for the development of novel antibacterial drugs. In the present study, antibacterial activity of novel 2-substituted benzimidazole derivatives (NR-1 to NR-9) was evaluated against three bacteria, viz. M. smegmatis, B. subtilis and E. coli using estimation of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Two (NR-4 and NR-5) exhibited inhibitory activity against M. smegmatis, while two (NR-5 and NR-7) were active against B. subtilis, with MICs ranging from 62.5 to 250 g/mL. Notably, NR-5 demonstrated antibacterial activity against both M. smegmatis and B. subtilis, with more efficacy against M. smegmatis (MIC: 62.5 g/mL) and bactericidal activity with an MBC/MIC ratio of 1. Cytotoxicity assessment in Vero cells indicated low toxicity for NR-4 and NR-5, and SwissADME evaluation suggested favourable physicochemical properties and drug-likeness. The growth kinetics profiling and time kill kinetics of the NR-5 Benzimidazole derivative demonstrated concentration-dependent activity, with complete growth suppression at 2x MIC. Additionally, checkerboard assay evaluation revealed a synergistic interaction of NR-5 with Rifampicin (FICI: 0.48), highlighting the enhanced antimycobacterial activity in combination. Molecular docking and binding-pocket analysis identified thymidylate kinase (tmk) as a potential target of NR-5. Thus, we have identified and characterised NR-5 as a promising benzimidazole-based antibacterial candidate that shows potent, low-toxicity antimycobacterial activity and works synergistically with rifampicin, making it a potential lead for future anti-tuberculosis drug development.